This application claims the priority of German application 197 03 788.7 filed Feb. 1, 1997 in Germany, and German application 197 14 763.1 filed Apr. 10, 1997 in Germany.
The invention relates to a slide rail for guiding and/or tensioning a chain, particularly for a camshaft drive of an internal-combustion engine, comprising a slide lining body and a carrier which each consist of a wear-resistant and mechanically highly stressable plastic material, the slide rail being held at a first position on the slide rail by means of a bolt received by a bush on a crankcase section of the internal-combustion engine and being provided with a supporting device at a second position on the slide rail spaced from the first position.
A known slide rail (German Patent Document DE-PS 37 06 136 corresponding to U.S. Pat. No. 4,832,669), which comprises a slide body and a carrier which are each made of plastic, has exhibited excellent results in practice in the case of the Porsche 911 Carrera Engine--Porsche Service Information--94, 911 Carrera, Illustration 649, specifically as a tensioning rail and also as a slide rail. In addition, while the stability is high under demanding load conditions, it was mainly found that the weight and the manufacturing costs are clearly lower than in the case of a conventional rail consisting of an aluminum carrier and a plastic rail lining body (German Patent Document DE-OS 35 06 010).
Based on the teaching of the above-mentioned practice-proven rail, it was suggested (German Patent Document DE 195 07 770 A1) to design the carrier and the rail lining body with a U-shaped cross-section on the side facing the chain. In this case, the slide lining body reaches behind the carrier on the legs of the U-shaped cross-section. This construction has the disadvantage that the U-shaped cross-section extends along a significant length of the rail which causes a high weight and also requires additional material. Furthermore, a slide rail with this selected cross-section required a relatively large amount of space which counteracts the endeavor to design the internal-combustion engine in a compact manner.
It is an object of the invention to further improve the technically proven slide rail, particularly with respect to its fastening on the internal-combustion engine.
According to the invention, this object is achieved by means of the characteristics of claim 1. Additional characteristics further developing the invention are contained in the following claims.
The principal advantages achieved by means of the invention are that, because of the supporting device consisting of the supporting section and the supported area, only a bolt and a bush are required for the teleologic (desired design position) holding of the slide rail. This further reduces the weight and the cost. An effective interaction between the supporting section and the supported area is achieved if the latter consists of a wear-resisting plastic material. The reason is that by this measure high loads are also securely absorbed over a long operating time, specifically by the material combination in which the supporting section is made of metal and the supported area is made of plastic. With respect to the manufacturing, the supporting section can be implemented in that it is manufactured of one piece with the slide lining body.
The line contact support ensures a defined function between the supporting section and the supported area and it can also be implemented by the concave design, preferably on the supported area.
The combination slide rail--slide lining body and support made of plastic--, single bolt, supporting device and projecting end of the slide rail permits a controlled chain travel in the case of which drive-caused movements of the chain based on the construction position can be effectively absorbed. This is also promoted by the local moment-of-resistance-increasing profiling.
The supported area is firmly connected with the slide body because the first web and the second web form a structural unit by means of ribs penetrating the carrier.
Transversely to the chain travel direction, the slide rail is fixed by a guiding device. In the bush of the carrier, a sleeve made of a wear-resistant plastic material is provided which represents a precision bore for the bolt constructed as a low-cost component.
Finally, the elastic damping device or spring device contributes to the fact that the slide rail is supported on the crankcase with little noise which is important in the case of internal-combustion engines with construction-type-specific operating characteristics, such as diesel engines.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.